Project Summary In this revised proposal, we plan to examine the physiological and synaptic properties of pluripotent stem cell (iPSC)-derived neurons, as well as schizophrenia (SCZ)-related physiological phenotypes, gathered from patients with 22q11 Deletion Syndrome (22q11DS). The syndrome associates with a 20-30 fold increase in the risk for schizophrenia. 20-30% of patients with 22q11DS develop SCZ by early adulthood. The acoustic startle response (ASR) is an evolutionarily conserved reflex, aspects of which differ in SCZ compared to healthy controls. Prior work on non-22q11DS individuals at high risk for SCZ based on their phenotypic characteristics (i.e., those with prodromal symptoms) suggest that the latency of ASR predicts conversion to SCZ. Mismatch negativity (MMN) is an evoked potential in response to unusual or ?oddball? acoustic stimuli imbedded within a train of repetitive acoustic stimuli. Impaired generation of an enhanced response to the oddball stimuli is the well-replicated MMN abnormality seen in SCZ. Our proposed work will examine ASR measures and MMN in older adolescents and young adults with 22q11DS (and healthy controls) to test the hypothesis that latency of the ASR and/or MMN will predict severity of prodromal symptoms, and ultimately conversion to SCZ, in this genetically defined high-risk group. Simultaneously we will study potential cellular mechanisms related to ASR and MMN in iPSC-derived neurons from 22q11DS patients exhibiting extreme values of latency to startle in the ASR. We hypothesize that doing so will identify potential cellular mechanisms underlying the phenotypic impact of the 22q11 deletion (including elevated risk for SCZ). This research will thus shed light on how genetic mechanisms alter cellular properties relevant to clinical and physiological differences observed in SCZ and the SCZ prodrome.